textproduct: Rapid City

KEY MESSAGES

- Active pattern persists through the week with daily chances of showers and thunderstorms.

- Severe weather expected Tuesday, especially from the Black Hills to northwest South Dakota. Large hail, damaging winds, and isolated tornadoes possible.

- Chance of severe weather with all hazards possible Thursday.

- Warming temperatures expected through the week into the weekend.

UPDATE

Issued at 1033 PM MDT Mon Jun 1 2026

Main focus with this update is the severe weather potential on Tuesday. Upper low along the central MT/Canadian border will continue to drift northwestward tonight and Tuesday. Ample moisture with southerly flow will again persist across the forecast area. However, surface obs show a surface trough/weak front/outflow boundary straddling southeast MT at this time. Strong convergence is supporting continued nocturnal storm development through Carter County in MT into the edge of Harding County and toward SW ND. Deep southerly low level flow now over the western SD plains...especially NW SD...will continue through Tuesday afternoon. The boundary will drift southeastward into the CWA and believe this is where the focus for convective development will be in the mid afternoon...from the Black Hills and the WY/SD border northward to NW SD. Models continue to show strong instability and effective bulk shear supporting supercell structure. The 0-1km shear is impressive near the boundary where surface winds may become even more easterly. HRRR/RAP show areas of heightening SigTor parameters in that area as well, but there is some differences with how much boundary layer moisture will be available. The CAMS suggested higher moisture/lower LCLs and an increased tornado threat. Will definitely be watching the trends overnight and in the morning to see how short term models resolve these features.

DISCUSSION

(This Evening Through Monday) Issued at 1218 PM MDT Mon Jun 1 2026

Water vapor imagery shows shortwave trough pushing through SE WY, NE CO, and the NE Panhandle with a closed upper low over northern MT. Southeasterly surface flow continues with weak moisture advection; low clouds around the Black Hills are eroding with diurnal heating and mixing ongoing.

Active southwest flow continues today with shortwave trough to eject through the region this afternoon and evening. Showers and thunderstorms will develop across the western half of the forecast area. Sufficient MUCAPE (~500-1000 J/kg) will be in place this afternoon as the boundary layer warms with effective bulk shear in excess of 45-50 knots. This combination will support the threat of severe weather from far NE WY through SW SD and the Black Hills. Forecast soundings show a well-mixed boundary layer with forecast DCAPE values ~800+ J/kg, supporting a wind threat with any stronger convection. Given the shear profiles, any robust updraft that gets rooted would have potential to produce large hail. Expect convection initiation around 21z this afternoon with the bulk of the convection and severe weather threat pushing east of our area after 02-04z.

Better severe weather threat exists across a more widespread area Tuesday as upper low begins to eject out of MT into southern Saskatchewan Tuesday afternoon. South-southeast low level winds will advect more substantial moisture into the area Tuesday. The result will be MLCAPE values around 1500-2500 J/kg Tuesday afternoon. The best overlap of instability with favorable shear will be from the central Black Hills to Rapid City and areas northward toward ND where effective bulk shear values around 35-50 knots are forecast. Convection is forecast to develop after 20-21z with supercellular structures possible. While there is some uncertainty regarding the depth and quality of moisture (and subsequent impact on tornado potential vs. more outflow dominant convection), all hazards will be possible Tuesday.

Active pattern persists through the week with daily chances of thunderstorms, with Thursday looking like the day where all ingredients best overlap. While much can change, Thursday has that look of a more classic northern Black Hills supercell day with ample shear, instability, southwest upper flow coupled with low-level moisture pooling/ESE flow around the northern Black Hills.

Upper level ridging is forecast to build over the region for the weekend with warm and generally dry conditions expected, at least for Saturday. More active pattern expected Sunday into early next week.

AVIATION

(For the 06Z TAFS Through 06Z Tuesday Night) Issued At 946 PM MDT Mon Jun 1 2026

A few lingering showers will be possible overnight but the main impacts to aviation weather will happen tomorrow.

While VFR conditions are mainly expected through the TAF period, another round of strong to severe thunderstorms is likely Tuesday afternoon into Tuesday evening. MVFR/IFR conditions are possible within the storms.

After the storms, the wind will shift to the west/northwest tomorrow night.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.